Billing code 45100: Rectal biopsyMedicare rate & RVUs in Washington
Transanal rectal biopsy obtains tissue for diagnosis, including evaluation of suspected Hirschsprung disease when a surgical tissue sample is needed.
CMS doesn’t publish an office rate for 45100 in Washington.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
On this page 9 sections
What 45100 covers
A surgeon reaches the rectum through the anus and removes tissue for pathologic examination. A common use is obtaining an adequate rectal sample when evaluating suspected Hirschsprung disease; colorectal, general, or pediatric surgeons may perform the procedure in an operating room or ambulatory surgery setting. This is distinct from taking a biopsy through a flexible endoscope.
Report the transanal biopsy when the operative record supports surgical access and tissue sampling from the rectum. Document the indication, approach, biopsy site, and specimens submitted for pathology. The 90-day global period includes the day-before preoperative visit and 90 days of related postoperative care. For other procedures performed in the same session, the highest-valued procedure is paid in full and other procedures are subject to the standard 50% multiple-procedure reduction. Modifier 50 is inappropriate. Medicare does not pay an assistant at surgery for this code; co-surgeons and team surgery are not permitted.
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
Where 45100 pays more and less in Washington
| Payment locality | Office | Facility |
|---|---|---|
| Rest Of Washington | Unavailable | $305.43 |
| Seattle (King Cnty) | Unavailable | $336.92 |
How the 45100 rate is calculated
Each of 45100’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.
How the rate is built · 45100
RVUs × geographic indexes × conversion factor
Swap in your local Medicare rate.
Work 3.94Practice expense 4.33Malpractice 0.78
All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.
Payment rules and modifiers for 45100
45100 has a 90-day global period: related visits in that window are included in the surgery payment.
CMS payment indicators · 45100
Rectal biopsy
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 090 | Major surgery: the day before, the day of, and 90 days after are included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 1 | Not paid (statutory restriction). |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
| Split (54/55/56) | 0.09/0.81/0.10 | Share of the payment for pre-op, the procedure itself, and post-op care. |
Global surgery period · 45100
Rectal biopsy
90-day global period ends
Dec 30, 2026
Covers Sep 30, 2026 through Dec 30, 2026 (92 days, including the day before surgery).
Visit on Oct 31, 2026
Day 30 of the 90-day post-op period: related follow-up care is included in the surgical payment.
Pre-op dayGlobal period
What modifiers do to the payment
Modifier 51 · payment effect
With and without the modifier
45100 without 51 · national facility
$302.28
Rectal biopsy
45100-51 · Second procedure: 50%
$151.14
When this isn’t the highest-valued procedure in the session, Medicare pays 50% of its fee schedule amount (the highest is paid at 100%).
45100 compared with similar codes
Compare codes
45100 vs 45331 vs 45380 vs 45160: national Medicare rates
Swap in your local Medicare rate.
How to choose
- 45331Sigmoidoscopy
- Use 45331 when a flexible sigmoidoscope is used to obtain the biopsy. Use 45100 for tissue sampling through transanal surgical access.
- 45380Colonoscopy with biopsy
- Use 45380 for biopsy performed during colonoscopy. The defining distinction is endoscopic access rather than transanal surgical access.
- 45160Rectal lesion excision
- 45160 describes transanal excision of a rectal lesion; 45100 describes obtaining biopsy tissue rather than excising the lesion.
45100 billing questions
How does this differ from an endoscopic rectal biopsy?
This code describes tissue sampling through transanal surgical access. A biopsy taken through a flexible sigmoidoscope or colonoscope is reported with the applicable endoscopy code instead.
Is this the usual code for a rectal biopsy to evaluate suspected Hirschsprung disease?
It can describe a transanal surgical biopsy obtained for that evaluation. The operative note should establish the transanal approach and rectal tissue sampling.
Can modifier 50 be used for biopsies on both sides?
No. CMS identifies bilateral adjustment as inappropriate for this code; do not append modifier 50.
How does the 90-day global period affect postoperative billing?
The day-before preoperative visit and 90 days of related postoperative care are included in the global period. The surgeon's documentation should distinguish care related to the biopsy from unrelated services.
Can an assistant surgeon or co-surgeon be reported?
Medicare does not pay an assistant at surgery for this code, and co-surgeons and team surgery are not permitted.
How are multiple procedures in the same session paid?
The highest-valued procedure is paid in full; other procedures in the session are subject to the standard 50% multiple-procedure reduction.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.
CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file lines behind this rate
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